Coating processes – Solid particles or fibers applied
Reexamination Certificate
1999-11-30
2001-09-04
Parker, Fred J. (Department: 1762)
Coating processes
Solid particles or fibers applied
C427S434500, C427S443200, C427S428010, C118S402000, C118S419000, C118S427000
Reexamination Certificate
active
06284310
ABSTRACT:
The present invention refers to a method and a apparatus for the preparation of monolayers of particles or molecules.
BACKGROUND OF THE INVENTION
The fabrication of monolayers of insoluble particles to the gas-liquid interface was realized through uses of troughs usually full of aqueous solutions. To the gas-water interface, solutions containing amphiphilic molecules are usually spreaded, these being molecules made of a polar head and a chain of fatty acids. After the volatile solvent has evaporated, it leaves at the gas-liquid interface the amphiphilic molecules. Finally, a mobile barrier compresses the molecules in a monolayer. Therefore, essentially there occurs an immobile trough containing an unmoving subphase or which molecules are laterally transported through it by exploiting the surface tension difference between the subphase and the deposited solution, and a mobile barrier.
The transfer of the monolayer onto a solid substrate is realized through several methods. One is the so-called Langmuir-Blodgett method, and essentially comprises a vertical immersion of a solid plate in the subphase through the monolayer; by pulling up such plate, the layer is transferred onto the plate by lateral compression. That can be repeated many times. Another method, called the Langmuir-Schaeffer method, comprises the descent of an horizontal plate onto the monolayer. After a contact is made, the plate is again extracted with the monolayer on it.
In order to improve the fabrication of insoluble particles, several attempts have been carried out. One has been to make a cylinder rotate under the water surface. One expected that such movement drove the insoluble particles ahead in a forming monolayer. However, in the majority of cases, this technique requires a precompression of an already prepared monolayer. The cylinder that compresses the layer is made of hydrophobic material. Moreover, only insoluble molecules are usable. Another device has been recently disclosed by G. Fuller, C. Franck and C. Robertson (Langmuir, 10, 1251 (1994)). It comprises the compression of insoluble particles with a flowing subphase between a fixed surface and the monolayer surfaces. Again, only insoluble molecules are used.
There are several limits in these previous methods: the essential one is that these methods are provided for insoluble particles. The attempts to extend the above methods to soluble particles have supplied marginal results. Slowness, loss of particles, low reproducibility and denaturation of proteins are a general characteristic of these methods.
The Applicant of the present invention and others disclosed a new method in the course of 1997 (Picard G., Nevernov I., Alliata D. and Pazdernick L., Langmuir, 13, 264 (1997)). The method has been marked with the acronym DTLF (Dynamic Thin Laminar Flow), and comprises a rotary cylinder that compresses a monolayer of soluble proteins. It was specifically planned in order to manufacture monolayers of soluble proteins, even if monolayers of soluble particles can also be easily realized. The features of this DTLF method are high-speed production, low amounts of materials being used, continuous production and preparation of bidimensional crystals. The newly prepared monolayer can also be deposited for further analysis on a solid, unmoving substrate. In other words, the device can be moved on a fixed substrate in order to deposit monolayers.
Even if in this study a machine has been disclosed that proved to be functional with proteins, the basic principles governing the DTLF method were not explained. This means that the use of such apparatus can be even useless if the basic forces are not controlled.
SUMMARY OF THE INVENTION
Object of the present invention is solving the above prior art problems, providing the basic principles for the DTLF method in such a way as to extend the application to the preparation of amorphous or crystalline monolayers of all kind of particles and their following transfer on any type of liquid or solid substrate.
A further object of the present invention is providing an apparatus for the simple, efficient and inexpensive realization of the above mentioned inventive method.
The basic principles of the DTLF method are based on the combination of three different processes. The first one is that it is necessary to use a thin liquid film: its thinness must be in the micrometer range. The second is the control of electrical charges of the particles in the thin liquid film in order to provoke the adsorption of particles to the gas-liquid interface without provoking the adsorption between them to the gas-liquid interface or in the thin liquid film itself. The third part is that, in order to create a force to drive particles against an edge for compression, the surface, on which there is the thin liquid film, is moved. This movement pushes the thin liquid film ahead and creates, through the liquid viscosity, a surface force that finally pushes particles ahead.
These and other objects are achieved according to the invention, the first embodiment of which includes a method for the preparation of a monolayer of particles or molecules, comprising:
injecting a thin liquid film containing said particles or molecules onto an external surface of a rotary member;
adjusting a surface charge density of said particles or molecules through the injection of an adsorption reagent, thereby carrying said particles or molecules to a gas-liquid interface of said thin liquid film;
forming a uniform monolayer of said particles or molecules on said gas-liquid interface;
transferring said monolayer from the gas-liquid interface to a solid substrate; and
moving said rotary number in a longitudinal direction relatively to said substrate, thereby separating said monolayer from said thin liquid film and adsorbing said monolayer to said substrate.
Another embodiment of the invention includes an apparatus for the preparation of a monolayer of particles or molecules, comprising:
a rotary member;
a motor;
an injection module having a plurality of openings;
a channel for injecting a thin liquid film;
a channel for injecting an adsorption reagent;
a channel connected to a suction pump; and
a substrate;
wherein said rotary member is actuated for forming a monolayer on a gas-liquid interface of a thin liquid film in contact with said substrate; and
wherein said rotary member can advance in a longitudinal direction with respect to said substrate.
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Nano World Projects Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Parker Fred J.
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